The present invention refers to an optical instrument for producing artificial rainbows which is used for a display in halls of entertainment or in shops or for an interior decoration. A comparatively small one can also be used as a toy.
One type of an optical instrument for producing artificial rainbows has already been employed to project a rainbow on walls or other places and to display a tasteful design with much novelty.
However, while a natural rainbow is an annulus in itself and appears to be a semicircular annulus to our sight, an artificial rainbow A produced by an already known optical instrument for producing artificial rainbows appears as an arc of a circle, as shown in FIG. 3, and its appearance is different from a natural rainbow because the intervals of each color are narrowed at each end of the artificial rainbow A.